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What Are Some Of The Common Bad Coil Pack Symptoms?

A pack of ignition coils that is a part of the ignition system in your car is a coil pack. A substitute to a coil pack in old vehicles was the distributors but these are not as reliable as coil packs. Coil Pack in a car is electronically controlled by the car’s computer. The function of the coil pack in a car is to build up energy by taking the 12-volt output from the battery and converting it to 45,000 volts then sending it to the spark plug cable to start the process of combustion.

The coil pack plays a very important role in this process and without it, the spark plug won’t reach its needed voltage to start a car. Thus it’s not desirable to have a faulty coil pack as it can affect your car’s performance a lot. In this article, we will be discussing bad coil pack symptoms so that you can easily identify them and do the necessary steps if your car gets a faulty coil pack.

Common Bad Coil Pack Symptoms

Coil Pack is one of the most important parts of your car and damage to it is undesirable. You may be unfamiliar with how you can identify whether your coil pack is faulty. So here are some bad coil pack symptoms.

1. Car Backfiring

One of the most common bad coil pack symptoms is car backfiring. A loud bang is produced as a result of the combustion happening inside the intake of the engine rather than the chamber. An explosion happens, due to this irregular combustion, inside the internal combustion engine or the exhaust, causing the loud bang.

This happens because your faulty coil pack can’t supply enough spark plug needed to complete the process properly. Due to the incomplete process, a fair amount of fuel will be left unused which goes out through the exhaust pipe. And this unused fuel may explode causing a loud bang and further emitting black poisonous smoke or a gasoline smell or fire from the exhaust.

If you notice any of this coming out of your exhaust or hear the bang frequently from your car, you can identify it as the issue of the coil pack. That’s your signal to take your car to your mechanic immediately and any delay to this can cause further damage to your car.

2. Poor Fuel Economy

You are probably aware of how much fuel your car needs and how long it lasts. But if you are noticing that your car is consuming more fuel than it used to lately, it could be having a bad coil pack.

If your coil pack is unable to produce enough power for the spark plugs, your vehicle tends to compensate it with fuel. This will make your car consume more fuel than it used to. So if you notice your car feeding itself more fuel, getting it checked by a mechanic will be helpful.

3. Engine Misfiring

One of the other bad coil pack symptoms is engine misfiring is, your car making noises that resemble cough like noises. You can also notice your car jerking while starting or idling around as a result of this symptom.

This issue is also caused a result of the coil pack not giving enough voltage to the spark plugs. Engine misfires can cause damage to other car parts due to the production of a lot of emissions. Thus it is best to take your car to a mechanic as soon as you start noticing such symptoms.

4. Drop Of RPMs During Acceleration

If you notice a huge drop in RPM while accelerating, you can conclude that your car’s coil pack is damaged. You can check your RPM level by looking at the RPM gauge when you drive.

5. Car Refusing To Start

A bad Coil pack can be one of the reasons that make your car refuse to start. If multiple ignition coils in your coil pack are damaged, no spark will be produced thus not letting the engine start. This is because your engine is not getting enough voltage from the coil pack to start. It is better to get your car checked by a mechanic immediately if it’s refusing to start.

6. Car Stalling

If you experience your car stalling while driving or when stopped, your coil pack may be faulty. This happens when the spark plug is getting unsteady electrical currents thus making your car unable to run smoothly. If your car is stalling, the coil pack may only be in the beginning stages of stalling so getting it fixed as soon as possible is the best thing to do to avoid further damage.

How To Test Your Coil Pack?

If you have experienced any of the above-mentioned symptoms, you’d want to further test your coil pack and see if it’s faulty. Here are some of the methods you can use to test your coil pack if you are a victim of bad coil pack symptoms.

  • You can, on your own, check your car’s coil pack and each ignition coil for any cracks, corrosion or burn marks. You can also make sure that there are no oil leaks inside the coil pack.
  • Another method you can use is checking the primary and secondary resistance of your coil pack using an ohmmeter.
  • Using a spark tester is another method you can use to check your coil pack. However, using the right quality tester is important as not all of them work well with the ignition system. Good spark testers can provide you with the right measurement of spark your coil pack produces, helping you determine whether it’s working well or not.

  • An oscilloscope is one of the best tools you can use to diagnose a coil pack problem. This tool measures the electrical signal in waveforms as it varies over time. However the tool is quite expensive but if you can pay some money, it is very effective.

Frequently Asked Questions:

So, here are some of the frequently asked questions about what problems would a faulty coil pack cause, what does bad coil pack sound like etc?-

What Problems Would A Faulty Coil Pack Cause?

A faulty ignition coil will cause your vehicle to misfire when you accelerate. A misfire could cause your vehicle to shut down. The misfire is a result of one of the cylinders’ fires being incorrect.

What Does Bad Coil Pack Sound Like?

A misfire occurs when, one or more combustion cylinders fail to combust the fuel-air mixture,  or spark plug. Often, misfires result in audible noises like sputtering noise.

How Do You Diagnose A Bad Coil Pack?

  1. An unexplainably louder-than-usual engine and a noticeable lack of power.
  2. An important drop in RPMs while accelerating for no reason.
  3. An intermittently activating check engine light.
  4. An active gas warning light when the vehicle has some gasoline.

Can A Bad Coil Cause Sputtering?

A sputtering or motion of the car is a sign of engine misfiring and this is a symptom of the ignition coil starting to fail. The gas mileage of your car also leads to problems.

Will A Bad Coil Throw A Code?

A bad ignition coil can cause several problems for your engine:

1. First you should check the engine light coming, if it detects a problem with an ignition coil, it will log any related trouble codes.

How Do You Test An Ignition Coil?

  1. First, you should plug the tester into the coil and attach the ground wire.
  2.  Then Plug in the coil connector.
  3. Adjust the spark gap and start the engine.
  4. If there’s a spark, great, it works and vice versa.


These bad coil pack symptoms are your car’s way of showing that you need to fix its cool pack soon. You can further use the techniques mentioned in the article to test your coil pack. This will help you determine how bad it needs maintenance or replacement. Delaying maintenance may not be a good idea as it can only cause further damage to your car and its other parts.